1. Field of Invention
The present invention relates to an electrical connection box which is suitable to be mounted on a vehicle, such as an automobile, and is adapted to have a relatively high voltage applied to it. The invention also relates to a vehicle including such an electrical connection box.
2. Description of Related Art
Normally one secondary, i.e. rechargeable, battery having a rated voltage of 12V and a maximum nominal voltage of 14V is mounted on an automobile of the internal combustion engine type. A voltage up to the maximum voltage of 14V is applied from the battery to a circuit composed of bus bars and the like that are accommodated in an electrical connection box. The power supply is distributed by the internal circuit of the electrical connection box. The operation of electric/electronic component parts mounted on the vehicle is controlled through electric wires connected with the internal circuit.
On a goods vehicle, such as a lorry or truck, a rated voltage of 24V and a maximum voltage of 28V are applied to a circuit by a battery structure.
In recent years, electric/electronic component parts have been mounted in increasing numbers on a vehicle, and there is an increase in the electric current which is applied to one electric/electronic component part. For example, the electric power required to drive a fan is conventionally 130 watts, but has become 260 watts in recent years. At the rated voltage of 12V of the battery, it is impossible to operate suction and exhaust devices of an engine, an electromotive power steering, and the like devices, requiring a high voltage such as 36V. Therefore, they are mechanically operated by the driving force of the engine.
With the increase of the electric current applied to each electric/electronic component part, the diameter of the electric wires used has become larger. Further, with rapid increase of the number of electric/electronic component parts, the number of electric wires has increased recently, which has increased the diameter of a wire harness having a bundle of electric wires. Consequently, the weight of the electric wires to be wired on a vehicle body has increased.
As described above, if the power supply from the battery is incapable of operating the suction and exhaust devices of the engine, they are mechanically operated. In this case, it is impossible to accomplish fine control of the operation of the suction and exhaust devices. Further much fuel is consumed, which pollutes the environment. Accordingly, it is preferable to operate the suction and exhaust devices of the engine and the like not mechanically but electrically by the power supply from the battery.
In the case where the circuit is so constructed that a voltage higher than 14V can be applied to the circuit of the electrical connection box composed of bus bars and the like, it is possible to reduce the required electric current and thus the diameter of the electric wires and the size of a bundle of a plurality of electric wires (wire harness). Therefore, it is possible to reduce the weight of the electric wires.
Further, with the application of a high voltage to the circuit composed of bus bars and the like, it is possible to control the operation of the suction and exhaust devices, the power steering motor, and the like not mechanically or hydraulically but electrically. In this case, it is possible to accomplish fine control of the operation of suction and exhaust devices and the like. Further, fuel consumption can be reduced, which reduces pollution.
It is preferable to apply a high voltage of about 42V to the electromotive power steering motor, the suction and exhaust devices of the engine, the fan, and other devices requiring a high voltage. On the other hand, in an automobile, it is preferable to apply the rated voltage of 12V (maximum voltage: 14V) to signal-generating devices of the electric/electrical components, parts and coils of relays.
However, if the electrical connection box for distributing the power supply is provided with a circuit to which a low voltage up to the maximum voltage of 14V (28V in a truck) is applied and with a circuit to which a high voltage of about 42V is applied, a leak current is liable to be generated between the two circuits owing to the potential difference. Such a leak current may particularly occur if water or dirt enters the electrical connection box. The leak current is also liable to be generated in the circuit to which the high voltage of about 42V is applied.
A leak current is liable to be generated between adjacent terminals in a connector attached to the electrical connection box, if the distance between the terminals is short, in the case where one of adjacent terminals disposed in a connector is connected to a bus bar to which a high voltage is applied and the other terminal is connected to a bus bar to which a low voltage is applied, and also in the case where two terminals disposed in the connector are connected to bus bars to which high voltages are applied.
The present invention seeks to mitigate the problem of leak currents in the connector described above. Therefore, it is an object of the present invention to prevent generation of leak currents in an electrical connection box which is provided with a circuit to which a low voltage is applied and a high voltage is applied, or a circuit to which a high voltage is applied.
According to the invention, there is provided an assembly comprising an electrical connection box and a connector. The electrical connection box has a casing having a connector-receiving portion adapted to receive a connector, at least one first bus bar mounted in the casing and having an upstanding connection tab, at least one second bus bar mounted in the casing and having an upstanding connection tab arranged alongside and spaced from the connection tab of the first bus bar, and insulation resin material embedding the connection tabs of said first and second bus bars while leaving exposed projecting portions thereof, the resin material further providing a recess located between the connection tabs.
The connector has first and second terminals engaged respectively to the projecting portions of the connection tabs of the first and second bus bars, and a housing in which the first and second terminals are mounted and which is received at the connector-receiving portion of said casing, the housing having a partition wall of insulating material which lies between the first and second terminals and extends into the recess of said insulation material.
In a first embodiment, the first bus bar is adapted to be connected in use to a first voltage source having a nominal maximum output voltage selected from 14V and 28V, and the second bus bar is adapted to be connected in use to a second voltage source having a nominal maximum output voltage higher than that of said first voltage source and not more than 200V.
In a second embodiment, the first and second bus bars are both adapted to be connected in use to a voltage source having a nominal maximum output voltage of not less than 14V, e.g. 28V or more.
It is preferable to embed each of the bus bars in an insulation body, such as an insulation plate which embeds the entire bus bar except projecting tab portion or portions thereof. For example, the root portion of each of the tabs is embedded in insulation resin, while portions of the tabs which fit in the terminals connected to electric wires are exposed.
The partition wall separates the terminals that are disposed in the connector and connected to the tabs, and extends to between the insulation resin portions covering the root portion of the tabs. Thus, it is possible to prevent a leak current from being generated between the adjacent terminals connected to the bus bars.
The bus bars may be fixed to a resin substrate by inserting a rib or spigot projecting from the substrate and deforming the rib, and then covering the substrate with a resin embedding the bus bars by molding.
It is preferable that the high voltage to be applied to the high-voltage bus bar is 42V. This is partly because it is easy to obtain a maximum nominal voltage of 42V by connecting in series three batteries each having a rated voltage of 12V (maximum voltage: 14V) of the type conventionally used in an automobile. Needless to say, it is possible to use a single battery having a maximum voltage of 42V. A second reason is because using a voltage close to 50V or above for the high-voltage bus bar is possibly dangerous. The present inventors have conducted salt water experiments in order to ascertain the degree of risk when applying a voltage of 42V in an electrical junction box suitable for use in an automobile engine compartment. Details of the experiments are given as follows:
1 ml of salt water was injected into each terminal hole of the casing of a junction box which had bus bars disposed inside. Electrical components such as relay, fuse, connectors, etc. were mounted on the casing. A voltage of 42V was applied to bus bars of the junction box for 8 hours and then suspended for 16 hours. This was repeated twice. There was initially no change to the bus bars and electrical components. After the third repetition, it was found that extra electric current passed between the bus bars generating heat, and a portion of bus bars was melted. The heat also melted resin around bus bars such as an insulation plate, casing and resin portion of electrical components adjacent the casing.
Accordingly, since damage did not occur until after the third exposure to salt water, it was confirmed that in consideration of conditions under normal use of an automobile, the application of the electric power at 42V to the electric/electronic component parts should not cause a problem.